Traveling from one location to another is one of the most important abilities of modern humans. For a large part of mankind's history, people were born, lived and died in a single, usually small, geographical area. The reason for this was, and in some parts of the world still is, because of a lack of transportation. While the development of the automobile is responsible for people having the ability to travel, a bicycle is also a very important contributing factor to the ability for individual travel. For many people throughout the world, a bicycle is preferable over an automobile or other vehicle. Some people simply can not afford an automobile while others embrace the health benefits and lack of any environmental damage caused by a bicycle. Bicycles have also become popular as means of exercise and also used for sporting events such as racing or BMX competition.
A typical bicycle is designed with two wheels/tires that are attached to a frame. The most common appearance of a bicycle frame is multiple inter-connected tubes usually made of metal. This type of frame design has long been in use, although there are negative aspects and problems inherent to the design. One of the problems is that a tube frame can experience a significant horizontal or out of plane flexing which is strongly felt by a person riding the bicycle. Another problem is that the use of tubes, which are limited in diameter, can produce a frame with limited structural stiffness and integrity.
What is needed is a bicycle frame that has greater torsional stiffness and fatigue life with approximately comparable vertical or in-plane stiffness as conventional tube frames. A beneficial alternative to a tube frame is a box beam frame which has equal mass and significantly greater structural benefits. A box beam frame does not experience the same level of flexing a tube frame. Further, the structural components of a box beam frame made of sheet material are low in cost, higher in strength, available in more alloys and are easily cut and formed. The components are readily attached together by strong and secure attachment means such as rivets, bonding or welding.
A box beam frame would offer solutions to many of the problems associated with a conventional tube frame, without presenting any new problems or deficiencies. The design is readily adaptable to any frame type including road, track, BMX, mountain and recreational use.
A search of the prior art did not disclose any literature or patents that read directly on the claims of the instant invention. However, the following U.S. patents are considered related:
PATENT NO.INVENTORISSUEDRe. 33,295TrimbleAug. 14, 19905,255,932MooreOct. 26, 19934,613,146Sharp, et alSep. 23, 19864,548,422Michel, et alOct. 22, 1985
The Re. 33,295 patent discloses a bicycle frame with a structural support that provided by a formed, stressed skin in conjunction with integral tubes and stiffening ribs. A body is formed which joins the front fork, pedal axle, seat post and rear wheel axle. The body is visually solid from the side with two open triangles of a conventional tube frame being filled in, and is airfoil shaped from the top. All control cables, and a cargo compartment, are contained within the frame.
The U.S. Pat. No. 5,255,932 discloses a superefficient bicycle frame having a plurality of dual tapered rectangular or square cross section frame members. A torsional-bending section modulus of a member is changed by providing a dual taper to the cross section of the frame members so that larger cross sections are used at points of greatest stress and smaller cross sections are used at points of lower stress. The method of manufacture is to cut various two dimensional shapes from sheet stock which are bent along nonparallel shapes from sheet stock which are bent along nonparallel bend lines to form the various members.
The U.S. Pat. No. 4,613,146 discloses a monocoque bicycle frame having a body having right and left side panels, top and bottom panels, and a bifurcated rearward portion defined by the panels and a rear wheel well insert. The body panels and insert enclose a continuous internal space which is compression loaded or tensile pre-stressed with a rigid foam plastic for increased torsional rigidity and resistance to impact distortion. A bicycle's pedal sprocket and chain are both external to the hollow frame so as to not interrupt the continuity of the body cavity and its compression loading, and also enabling the body to have minimal weight and an optimum aerodynamic configuration. The frame is diamond-shaped in side profile thus enabling the monocoque to be constructed as a pair of triangles connected back-to-back both torsionally and against vertical loading.
Comparing the instant invention with the U.S. Pat. No. 4,613,146 prior art patent:
1) Racing bicycle frames must be less than 3.5 pounds to compete. Even the lightest structural foam is 2 pounds per cubic foot so the minimum weight that would be added in the prior art design would be a pound or more.
2) The prior art design does not take advantage of lightening holes used in formers on aircraft; the instant invention does. This method results in an obvious weight advantage.
3) The prior art connecting flange is impossible to form from high-strength material, thus the flange would have to be formed of soft aluminum capable of being heat treated. Therefore, the number of materials which could be used is greatly limited, unlike the instant invention.
The U.S. Pat. No. 4,548,422 discloses a bicycle frame having a shell structure consisting of two assembled shells. Each shell has the axis of a passage of a seat shaft combined with the axis of a housing of a crank gear in the plane of assembly.
For background purposes and indicative of the art to which the invention relates, reference may be made to the following remaining patents found in the patent search.
PATENT NO.INVENTORISSUED4,230,332PorscheFeb. 14, 19973,375,024GeorgeFeb. 8, 19662,855,20Douglas, et alJun. 20, 19575,470,092FardyNov. 28, 1995